https://www.jiqizhixin.com/articles/2019-04-19-20
Only state transition Markov state transition probabilities, initial state probability
Hidden Markov has state, state transition probabilities, initial state probability, probability distribution status output, output set of characters
hmm often 3 problem: given a sequence of O, find the probability of occurrence; given a sequence of O, it is optimized so that the maximum probability; hmm seeking a maximum output sequence;
Seeking maximum output sequence, i.e., it uses a viterbi algorithm;
